CHECK YOUR PASSMARK SCOREPlease type in the name/series of your graphics card in the search field in the top right corner on the following page (eg, "Nvidia 560Ti"), and make a note of the number of PassMark points your graphics card has:http://www.videocardbenchmark.net

There is more kind of GTX660 so I am just curious which one is all right.

for example

GIGABYTE GV-N66TOC-2GD GTX660 2GB PCIE

NVIDIAÂ® CUDAâ„¢ technology unlocks the power of the hundreds of cores in your NVIDIAÂ® GeForceÂ® graphics processor (GPU) to accelerate some of the most performance hungry computing applications. The CUDAâ„¢ technology already adopted by thousands of programers to speed up those performance hungry computing applications.

NVIDIAÂ® 3D Visionâ„¢ brings a fully immersive stereoscopic 3D experience to the PC. A combination of high-tech wireless glasses and advanced software 3D Vision transforms hundreds of PC games into full stereoscopic 3D. Users can even watch 3D movies and 3D digital photographs in crystal-clear quality.

NVIDIAÂ® CUDAâ„¢ technology unlocks the power of the hundreds of cores in your NVIDIAÂ® GeForceÂ® graphics processor (GPU) to accelerate some of the most performance hungry computing applications. The CUDAâ„¢ technology already adopted by thousands of programers to speed up those performance hungry computing applications.

Always depends on your budget, but sometimes spending a little extra for the extra bang is worth it, after all, in most cases its an investment, not a cost and is easily recovered through time savings etc.

Would suggest have a look at the GTX670 (preferably the overclocked factory version), priced slightly more than the 660 and a bit faster, but seems to be close in performance to the 680 but much more affordable (at least down here). Long period rendering for a factory based overclock should be fine, just not recommended to up the clock on standard versions.